Temperature-responsive device

ABSTRACT

A temperature-responsive device ( 14 ) is provided for an electric heater ( 2 ). The heater ( 2 ) is located behind a heatable surface and comprises a dish-like support ( 6 ) having therein at least one electric heating element ( 12 ) having first and second terminal regions, ( 12 A,  12 B). An electrical component ( 18 ), having an electrical parameter which changes as a function of temperature, is supported inside the heater ( 2 ) by an elongate member ( 16 ). The elongate member ( 16 ) is secured to the heater ( 2 ) and extends at least partially across the heater ( 2 ). An electrically insulating carrier member ( 30 ) is secured to the elongate member ( 16 ) at a location externally of the periphery of the heater ( 2 ). The carrier member ( 30 ) has first and second side edges ( 32, 38 ) at opposite sides of the elongate member ( 16 ) and is provided with first and second electrically conductive elements ( 34, 40 ) accessible at the opposite side edges ( 32, 38 ) for electrical connection to the first and second terminal regions ( 12 A,  12 B).

This invention relates to an electric heater provided with atemperature-responsive device, for example an electric heater for use ina cooking appliance, such as a cooking hob having a glass-ceramiccooking surface.

It is well known to provide a temperature-responsive device forcontrolling operation of an electric heater. Such an electric heater istypically arranged for location behind a surface to be heated, such as aglass-ceramic cooking surface, and generally comprises a dish-likesupport having therein at least one electric heating element. Inparticular, the temperature-responsive device comprises an electricalcomponent having an electrical parameter which changes as a function oftemperature and which is supported by an elongate member which isarranged to extend at least partly across the heater from a peripherythereof. The electrical component provides an electrical output whichchanges as a function of temperature, the electrical component beingelectrically connected to an electronic controller, such as amicroprocessor-based controller, to control energising of the electricheater from a power supply.

In particular, the electrical component comprises an electricalresistance temperature detector, such as a platinum resistancetemperature detector, whose electrical resistance changes as a functionof temperature. The electrical component may be supported inside a tube,such as of metal or ceramic, or on an elongate beam, such as of ceramicmaterial.

It is known to provide a terminal block externally on the dish-likesupport of the heater. Such terminal block is remote from thetemperature-responsive device and is connected inside the heater toterminal regions of the heating element or elements. External leads arearranged from the terminal block to the power supply, suitably by way ofthe electronic controller.

It is also known to provide direct electrical connection betweenterminal regions of a heating element and connecting elements on atemperature-limiting device, such connecting elements being accessiblein the region of a front face of a switch housing of thetemperature-limiting device adjacent to the heater. In this knownarrangement, the temperature-limiting device comprises adifferentially-expanding rod and tube assembly, which extends at leastpartly across the heater from the housing and operates one or moreswitch means located in the housing.

It is an object of the present invention to provide an electricalconnection between terminal regions of a heating element and electricalconducting elements on a temperature-responsive device of an electricheater which overcomes or at least ameliorates disadvantages of theabove arrangements.

According to the present invention there is provided an electric heateradapted for location behind a surface to be heated and comprising adish-like support having therein at least one electric heating elementhaving a first terminal region and a second terminal region and atemperature-responsive device, wherein the temperature-responsive devicecomprises an electrical component having an electrical parameter whichchanges as a function of temperature and arranged to be supported insidethe heater by an elongate member which is adapted to be secured to theheater and to extend at least partially across the heater from a regionexternally of the periphery thereof, an electrically insulating carriermember being secured to the elongate member at a location externally ofthe periphery of the heater, the carrier member having a first side edgeand a second side edge laterally disposed at opposite sides of theelongate member and provided with a first electrically conductiveelement and a second electrically conductive element accessible at theopposite side edges of the carrier member for electrical connection tothe first and second terminal regions respectively of the at least oneelectric heating element.

Electrical connection of the first and second electrically conductiveelements to the respective first and second terminal regions of the atleast one heating element may be by means of direct contact between theelectrically conductive elements and the terminal regions.

The first and second terminal regions of the at least one heatingelement may extend through apertures in the dish-like support forelectrical connection to the first and second electrically conductiveelements.

The first and second terminal regions of the at least one heatingelement may be electrically connected to the first and secondelectrically conductive elements by welding.

At least one of the first and second electrically conductive elementsmay be provided with a portion selected from a strip-like portion and aflanged portion for securing to at least one of the first and secondterminal regions of the at least one heating element.

The strip-like portion may have a plane thereof disposed in any desiredorientation from a vertical plane to a horizontal plane.

The flanged portion may have a wall portion with a dependantlaterally-directed ledge portion.

At least one of the first and second electrically conductive elementsmay have the portion extending in a direction towards the heater and ata predetermined angle relative to a rim of the dish-like support.

Alternatively, at least one of the first and second electricallyconductive elements may be arranged for electrical connection to aterminal region selected from the respective first and second terminalregions of the at least one heating element by way of at least oneelectrically conductive link, for example of a form selected from wireand strip form.

The at least one electrically conductive link may extend throughapertures in the dish-like support for electrical connection to thefirst and second electrically conductive elements.

The at least one electrically conductive link may be electricallyconnected to the first and second electrically conductive elements bywelding.

At least one of the first and second electrically conductive elementsmay be provided with a portion selected from a strip-like portion and aflanged portion for securing to the at least one electrically conductivelink.

The strip-like portion may have a plane thereof disposed in any desiredorientation from a vertical plane to a horizontal plane.

The flanged portion may have a wall portion with a dependantlaterally-directed ledge portion.

At least one of the first and second electrically conductive elementsmay have the portion extending in a direction towards the heater and ata predetermined angle relative to a rim of the dish-like support.

The first and second electrically conductive elements may extendlaterally at the first and second opposite side edges of the carriermember.

The at least one electric heating element may be of corrugated ribbonform supported upstanding on edge in the dish-like support.

At least one of the first and second terminal regions of the at leastone electric heating element of corrugated ribbon form may be connecteddirectly to at least one of the first and second electrically conductiveelements and have an orientation substantially the same as that of theat least one electric heating element as supported in the dish-likesupport, or may be twisted through an appropriate angle for connectionto at least one of the first and second electrically conductiveelements.

The first and second electrically conductive elements may comprisemetal, such as stainless steel or nickel-plated steel.

The first and second electrically conductive elements may be providedwith means for electrical connection thereof to external lead wires.Such means for electrical connection may comprise terminal members, suchas of tab or spade form.

The carrier member may comprise ceramic material.

The electrical component may be provided with electrical leads extendingtherefrom and emerging from the elongate member at the region of theheater externally of the periphery thereof. Such electrical leads may beadapted to be electrically connected to an electronic controller, suchas a microprocessor-based controller, which is adapted to providecontrolled electrical connection between a power supply and the firstand second electrically conductive elements.

The electrical component may comprise a device whose electricalresistance changes as a function of temperature, and may comprise anelectrical resistance temperature detector, such as a platinumresistance temperature detector.

The elongate member may comprise a tube, such as of metal or ceramic,inside which the electrical component is arranged.

Alternatively, the elongate member may comprise a beam, such as ofceramic material, on a surface of which the electrical component isprovided.

For a better understanding of the present invention and to show moreclearly how it may be carried into effect, reference will now be made,by way of example, to the accompanying drawings in which:

FIG. 1 is a plan view of an arrangement of part of an electric heateraccording to the present invention provided with an embodiment of atemperature-responsive device; and

FIG. 2 is a plan view of a modification of the arrangement of FIG. 1.

Referring to FIG. 1, an electric heater 2 is arranged for locationbeneath a surface 4 to be heated. The surface 4 may be a cooking surfaceand may comprise glass-ceramic material.

The heater 2 comprises a dish-like support 6, such as of metal,containing a layer 8 of thermal and electrical insulation material, suchas microporous thermal and electrical insulation material. A peripheralwall 10 of thermal insulation material is provided in the dish-likesupport 6 and contacts the underside of the surface 4 to be heated.

At least one radiant electric heating element 12 is arranged inside thedish-like support 6. As shown in FIG. 1, heating element 12 comprises acorrugated metal ribbon arranged upstanding on edge in the dish-likesupport 6. However, other forms of heating element could be provided.

A temperature-responsive device 14 is provided for the heater 2 andcomprises an elongate member 16 which is suitably secured to the heaterat the periphery thereof and extends from a region externally of theperiphery of the heater, through an aperture in the rim of the dish-likesupport 6 and the peripheral wall 10, and at least partially across theheater. The elongate member 16 is arranged to overlie and be spaced fromthe at least one heating element 12.

The elongate member 16 supports an electrical component 18 having anelectrical parameter which changes as a function of temperature andwhich is provided with electrically conducting leads 20 which extendtherefrom and emerge from the elongate member 16 at an end 22 thereofwhich is located externally of the heater 2. The electrical component 18suitably comprises a device whose electrical resistance changes as afunction of temperature and may comprise an electrical resistancetemperature detector, such as a platinum resistance temperaturedetector.

The elongate member 16 may comprise a tube, such as of metal or ceramic,inside which the electrical component 18 is arranged at one end 24thereof, and with the leads passing along the tube. Alternatively, theelongate member 16 may comprise a beam, such as of ceramic, on an uppersurface of which the electrical component 18 is arranged at one end 24thereof. In this case, the electrical component 18 and/or the portion ofthe leads extending therefrom along the beam 16, may be of film form,deposited on the surface of the beam 16, although this is not essential.

The leads 20 from the electrical component 18 are arranged to beelectrically connected to a microprocessor-based electronic controller26, which is electrically connected to a power supply 28.

A carrier member 30 of electrically insulating material, such asceramic, is secured to the elongate member 16 externally of the heaterat the end 22 of the elongate member 16. The carrier member 30 issuitably of block form and is suitably provided with an aperture throughwhich the elongate member 16 passes. The carrier member may form aninterference fit with the elongate member 16 or may be secured theretoby adhesive or other means.

The carrier member 30 has a first side edge 32 at which laterallyextends a first electrically conductive element 34 having a portion 36extending in a direction towards the heater at a predetermined anglerelative to the rim of the dish-like support 6.

The carrier member 30 has a second side edge 38 at which laterallyextends a second electrically conductive element 40 having a portion 42extending in a direction towards the heater at a predetermined anglerelative to the rim of the dish-like support 6.

The first electrically conductive element 34 is provided with a terminalmember 44, such as of tab or spade form, arranged for electricalconnection to an external lead wire 46 provided from the power supply 28by way of the controller 26. The second electrically conductive elementis likewise provided with a terminal member 48, such as of tab or spadeform, arranged for electrical connection to an external lead wire 50provided from the power supply 28 by way of the controller 26.

The first and second electrically conductive elements 34, 40 aresuitably secured to the carrier member 30 by means 35, 41, which maycomprise rivets. Alternatively, other fastening means such as twisttabs, welding or discrete fasteners such as drive screws of standardscrews and nuts may be employed.

The first and second electrically conductive elements 34 and 40 areaccessible at the side edges 32, 38 of the carrier member 30 andsuitably comprise metal, such as stainless steel or nickel-plated steel.They are suitably of strip form.

The corrugated ribbon heating element 12 has first and second terminalregions 12A and 12B thereof extending through apertures 52, 54 in theperipheral wall 10 and the rim of the dish-like support 6, of the heater2. If desired, the terminal regions 12A and 12B need not be corrugated.The first terminal region 12A of the heating element 12 is weldeddirectly to the portion 36 of the first electrically conductive element34 and the second terminal region 12B of the heating element 12 iswelded directly to the portion 42 of the second electrically conductiveelement 40. The first and second electrically conductive elements 34, 40are readily accessed at the side edges 32, 38 of the carrier member 30by the jaws of a pincer welding apparatus (not shown), to effect thenecessary welding operations.

The portions 36 and 42 of the first and second electrically conductiveelements 34, 40 may comprise wall portions and have dependantoutwardly-directed ledge portions 36A and 42A respectively, such thatthe first and second electrically conductive elements 34, 40 have aresultant flanged form. The ledge portions 36A and 42A serve to supportthe first and second terminal regions 12A, 12B of the heating element 12during the welding operation and may each be provided with an upstandinglip (not shown) on the outer edge thereof to assist retention of theterminal regions 12A, 12B on the ledge portions 36A, 42A prior towelding. The lips may extend upwardly by about 2 mm and such that theydo not inhibit access by the welding apparatus. Alternatively, othermeans (not shown) may be provided to retain the terminal regions 12A,12B on the ledge portions 36A, 42A prior to welding.

The portions 36 and 42 of the first and second electrically conductiveelements 34, 40 could be of simple strip form, having a plane thereofdisposed in any desired orientation from a vertical plane to ahorizontal plane.

When the heater 2 is energised for operation, heat is sensed by theelectrical component 18 and its electrical parameter, such as electricalresistance, changes as a function of temperature. The change in theelectrical parameter is monitored by the controller 26, which operatesin known manner to control energising of the at least one heatingelement 12 from the power supply 28, through the lead wires 46, 50, andprovide a desired heating rate and/or temperature limit for the heater.

As shown in FIG. 1, the first and second terminal regions 12A, 12B ofthe corrugated ribbon heating element 12 have an orientationsubstantially the same as that of the heating element 12 as supported inthe dish-like support 6. If desired, however, the first and/or secondterminal region or regions 12A, 12B of the heating element 12 may betwisted through an appropriate angle for connection to the first and/orsecond electrically conductive elements 34, 40 in a different plane.This is illustrated in FIG. 2, where the first terminal region 12A ofthe heating element 12 is twisted and welded to the outwardly-directedledge portion 36A of the portion 36 of the first electrically conductiveelement 34. The second terminal region 12B of the heating element 12 canbe similarly arranged.

Instead of the first and second terminal regions 12A, 12B of the heatingelement 12 being directly welded to the first and second electricallyconductive elements 34, 40, one or more intermediate electricallyconductive links, such as of wire or strip form, may be providedconnecting the first and/or second terminal regions 12A, 12B of theheating element 12 to the first and/or second electrically conductiveelements 34, 40 respectively. This is illustrated in FIG. 2, where thesecond terminal region 12B of the heating element 12 is welded to oneend of a link 56 inside the heater 2. The link 56 passes throughaperture 54 in the peripheral wall 10 and the rim of the dish-likesupport 6 of the heater 2 and is welded at its opposite end to theportion 42, or the portion 42A, of the second electrically conductiveelement 40. The first terminal region 12A of the heating element 12 canbe similarly treated.

The provision of one or more electrically conductive links, such as thelink 56, is particularly advantageous when a heating element of lampform is provided instead of the ribbon heating element 12 and whereterminals on an envelope of the lamp cannot be connected directly to thefirst and second electrically conductive elements 34, 40.

Although specific reference has been made to an electrical component 18in the form of an electrical resistance temperature detector, such as aplatinum resistance temperature detector, the electrical component 18could comprise any other suitable device having an electrical parameterwhich changes as a function of temperature. For example, the component18 could comprise a thermistor or a thermocouple, or a device whoseelectrical capacitance or inductance appropriately changes as a functionof temperature.

It is to be noted that no electrical connections are provided, on thetemperature responsive device 14, between the first and secondelectrically conductive elements 34, 40 on the carrier means 30 and theelectrical component 18 supported by the elongate member 16.

1. An electric heater (2) adapted for location behind a surface to beheated and comprising a dish-like support (6) having therein at leastone electric heating element (12) having a first terminal region (12A)and a second terminal region (12B) and a temperature-responsive device(14), wherein the temperature-responsive device comprises an electricalcomponent (18) having an electrical parameter which changes as afunction of temperature and arranged to be supported inside the heater(2) by an elongate member (16) which is adapted to be secured to theheater (2) and to extend at least partially across the heater (2) from aregion externally of the periphery thereof, an electrically insulatingcarrier member (30) being secured to the elongate member (16) at alocation externally of the periphery of the heater (2), the carriermember (30) having a first side edge (32) and a second side edge (38)laterally disposed at opposite sides of the elongate member (16) andprovided with a first electrically conductive element (34) and a secondelectrically conductive element (40) accessible at the opposite sideedges (32, 38) of the carrier member (30) for electrical connection tothe first and second terminal regions (12A, 12B) respectively of the atleast one electric heating element (12).
 2. An electric heater asclaimed in claim 1, wherein electrical connection of the first andsecond electrically conductive elements (34, 40) to the respective firstand second terminal regions (12A, 12B) of the at least one heatingelement (12) is by means of direct contact between the electricallyconductive elements (34, 40) and the terminal regions (12A, 12B).
 3. Anelectric heater as claimed in claim 1, wherein the first and secondterminal regions (12A, 12B) of the at least one heating element (12)extend through apertures in the dish-like support (6) for electricalconnection to the first and second electrically conductive elements (34,40).
 4. An electric heater as claimed in claim 1, wherein the first andsecond terminal regions (12A, 12B) of the at least one heating element(12) are electrically connected to the first and second electricallyconductive elements (34, 40) by welding.
 5. An electric heater asclaimed in claim 1, wherein at least one of the first and secondelectrically conductive elements (34, 40) is provided with a portion(36, 42) selected from a strip-like portion and a flanged portion forsecuring to at least one of the first and second terminal regions (12A,12B) of the at least one heating element (12).
 6. An electric heater asclaimed in claim 5, wherein the strip-like portion has a plane thereofdisposed in any desired orientation from a vertical plane to ahorizontal plane.
 7. An electric heater as claimed in claim 5, whereinthe flanged portion has a wall portion with a dependantlaterally-directed ledge portion (36A, 42A).
 8. An electric heater asclaimed in claim 5, wherein at least one of the first and secondelectrically conductive elements (34, 40) has the portion (36, 42)extending in a direction towards the heater (2) and at a predeterminedangle relative to a rim of the dish-like support (6).
 9. An electricheater as claimed in claim 1, wherein at least one of the first andsecond electrically conductive elements (34, 40) is arranged forelectrical connection to a terminal region selected from the respectivefirst and second terminal regions (12A, 12B) of the at least one heatingelement (12) by way of at least one electrically conductive link (56).10. An electric heater as claimed in claim 9, wherein the at least oneelectrically conductive link (56) is of a form selected from wire andstrip form.
 11. An electric heater as claimed in claim 9, wherein the atleast one electrically conductive link (56) extends through apertures inthe dish-like support (6) for electrical connection to the first andsecond electrically conductive elements (34, 40).
 12. An electric heateras claimed in claim 9, wherein the at least one electrically conductivelink (56) is electrically connected to the first and second electricallyconductive elements (34, 40) by welding.
 13. An electric heater asclaimed in claim 9, wherein at least one of the first and secondelectrically conductive elements (34, 40) is provided with a portion(36, 42) selected from a strip-like portion and a flanged portion forsecuring to the at least one electrically conductive link (56).
 14. Anelectric heater as claimed in claim 13, wherein the strip-like portionhas a plane thereof disposed in any desired orientation from a verticalplane to a horizontal plane.
 15. An electric heater as claimed in claim13, wherein the flanged portion has a wall portion with a dependantlaterally-directed ledge portion (36A, 42A).
 16. An electric heater asclaimed in claim 9, wherein at least one of the first and secondelectrically conductive elements (34, 40) has the portion (36, 42)extending in a direction towards the heater (2) and at a predeterminedangle relative to a rim of the dish-like support (6).
 17. An electricheater as claimed in claim 1, wherein the first and second electricallyconductive elements (34, 40) extend laterally at the first and secondopposite side edges (32, 38) of the carrier member (30).
 18. An electricheater as claimed in claim 1, wherein the at least one electric heatingelement (12) is of corrugated ribbon form (12) supported upstanding onedge in the dish-like support (6).
 19. An electric heater as claimed inclaim 18, wherein at least one of the first and second terminal regions(12A, 12B) of the at least one electric heating element (12) ofcorrugated ribbon form (12) is connected directly to at least one of thefirst and second electrically conductive elements (34, 40) and has anorientation substantially the same as that of the at least one electricheating element (12) as supported in the dish-like support (6).
 20. Anelectric heater as claimed in claim 18, wherein at least one of thefirst and second terminal regions (12A, 12B) of the at least oneelectric heating element (12) of corrugated ribbon form (12) isconnected directly to at least one of the first and second electricallyconductive elements (34, 40) and is twisted through an appropriate anglefor connection to at least one of the first and second electricallyconductive elements (34, 40).
 21. An electric heater as claimed in claim1, wherein the first and second electrically conductive elements (34,40) comprise metal.
 22. An electric heater as claimed in claim 21,wherein the metal is selected from stainless steel and nickel-platedsteel.
 23. An electric heater as claimed in claim 1, wherein the firstand second electrically conductive elements (34, 40) are provided withmeans for electrical connection thereof to external lead wires (50). 24.An electric heater as claimed in claim 23, wherein the means forelectrical connection comprises terminal members (44, 48).
 25. Anelectric heater as claimed in claim 24, wherein the terminal members(44, 48) are of a form selected from tab and spade form.
 26. An electricheater as claimed in claim 1, wherein the carrier member (30) comprisesceramic material.
 27. An electric heater as claimed in claim 1, whereinthe electrical component (18) is provided with electrical leads (20)extending therefrom and emerging from the elongate member (16) at theregion of the heater (2) externally of the periphery thereof.
 28. Anelectric heater as claimed in claim 27, wherein the electrical leads(20) are adapted to be electrically connected to an electroniccontroller (26) which is adapted to provide controlled electricalconnection between a power supply (28) and the first and secondelectrically conductive elements (34, 40).
 29. An electric heater asclaimed in claim 28, wherein the electronic controller (26) is amicroprocessor-based controller (26).
 30. An electric heater as claimedin claim 1, wherein the electrical component (18) comprises a devicewhose electrical resistance changes as a function of temperature.
 31. Anelectric heater as claimed in claim 1, wherein the electrical component(18) comprises an electrical resistance temperature detector.
 32. Anelectric heater as claimed in claim 31, wherein the electricalresistance temperature detector is a platinum resistance temperaturedetector.
 33. An electric heater as claimed in claim 1, wherein theelongate member (16) comprises a tube inside which the electricalcomponent (18) is arranged.
 34. An electric heater as claimed in claim33, wherein the tube is of a material selected from metal and ceramic.35. An electric heater as claimed in claim 1, wherein the elongatemember (16) comprises a beam on a surface of which the electricalcomponent (18) is provided.
 36. An electric heater as claimed in claim35, wherein the beam is of ceramic material.
 37. (canceled)